1. Field of the Invention
The present invention relates to airtight waterproof slide fastener, which is employed at a portion demanding airtight waterproof performance under high pressures such as in diving suits and underwater tunnels.
2. Description of the Related Art
Engagement teeth for the airtight waterproof slide fastener provided currently are largely divided into two types of structures, which are an engagement tooth structure disclosed in, for example, Germany Patent No. 856881, Japanese Utility Model Application Laid-Open No. 58-181210, and Japanese Patent Application Publication No. 63-8763, and an engagement tooth structure disclosed in, for example, Japanese Patent Application Publication No. 1-54041, Japanese Patent Application Publication No. 2-16648, and Japanese Utility Model Application Publication No. 5-2098. Composing elements of these engagement teeth include a spear-shaped coupling element having a coupling head at its front end and a substantially U-shaped clamp element having a nipping portion composed of a pair of small sheet pieces and a connecting portion for connecting end portions thereof. This clamp element is usually obtained by fastening a rectangular sheet piece into a substantially U-letter shape.
According to the engagement tooth structure disclosed in the above-mentioned Germany Patent No. 856881, Japanese Utility Model Application Publication No. 58-181210, and Japanese Patent Application Publication No. 63-8763, the coupling element is so constructed as to be directed from the center of the inside of the connecting portion of the clamp element such that the coupling head is exposed out and protruded integrally therewith. In order to fix this engagement teeth to the airtight waterproof fastener tape, insertion holes for the coupling heads are formed at a predetermined pitch along a side edge of this airtight waterproof tape and the coupling head of the engagement tooth is passed through this hole. Then, the airtight waterproof tape is bent and pushed in the shape of xcexa9 such that the insertion hole forming portion makes a firm contact with a curved bottom of the clamp element and then, the clamp element is fastened from both front and rear sides so as to nip the tape firmly in order to produce the airtight waterproof fastener stringer.
On the other hand, according to the structure of the engagement tooth disclosed in the Japanese Patent Application Publication No. 1-54041, Japanese Patent Application Publication No. 2-16648, and Japanese Utility Model Application Publication No. 5-2098, a coupling element comprising a coupling head at a front end thereof and an spear-shaped coupling element having a rectangular flange at the rear end thereof, and a substantially U-shaped clamp element are formed separately. To fix the engagement tooth onto the airtight waterproof tape, a side edge portion of the airtight waterproof tape is wound around from the flange side to the coupling head at the front end such that it wraps and holds the coupling element. Then, the clamp element is held through the airtight waterproof tape from the flange side of the coupling element up to just before the coupling head and fastened strongly so that the tape wraps and holds the clamp element. Consequently, the side edge portion of the airtight waterproof tape is bent in the shape of xcexa9 by means of the clamp element, so that the tape is nipped and fixed firmly, thereby an airtight waterproof fastener stringer is produced.
Air-tightness and waterproofness of these airtight waterproof slide fasteners is warranted by contact pressing force of the airtight waterproof tape portion which is bent and exposed outward between the coupling head of each of a pair of opposing fastener stringers and the clamp element. If this contact pressing force is weak, gap is generated between the tapes pressing each other, by hydraulic pressure or other external forces applied to the airtight waterproof tape.
By the way, in the above-described engagement tooth comprising integrated coupling element and clamp element, management of parts is facilitated because the number of required parts is reduced. However, to fix the engagement tooth to the airtight waterproof tape, insertion holes for the coupling heads need to be formed in the side edge portion of the airtight waterproof tape. Further, after inserting the coupling head into the insertion hole, it is necessary to push the tape toward the bottom face of the clamp element so that it is bent in the shape of letter U. Consequently, this fixing structure allows the airtight waterproof tape to move easily in the width direction of the tape, so that the nipping and fixing force by the clamp element tends to weaken. Thus, as described in Japanese Utility Model Application Laid-Open No. 58-181210, a lip for nipping the tape is projected from opposing faces at open side end portions of the clamp element so as to increase the fixing strength of the engagement tooth to the airtight waterproof tape.
For the airtight waterproof slide fastener of this type, securing its airtight waterproof performance depends upon contact pressing force between opposing tape portions when opposing engagement teeth of a pair of fastener stringers are coupled. Then, if a tongue piece is formed such that it is projected outward at right angle from one end or both ends of front and rear sides of the clamp element bent in a substantially U shape so as to increase the contact area, necessary contact pressing force is secured such that necessary airtight waterproof performance is easily obtained. However, formation of the tongue piece such that it is projected outward of the clamp element increases the thickness of the entire slider, which is a fastener opening/closing device, in a direction perpendicular to the airtight waterproof tape.
On the other hand, in the structure of the engagement tooth comprising a coupling element and a clamp element formed separately as indicated by the above Japanese Patent Application Publication No. 1-54041, Japanese Patent Application Publication No. 2-16648 and Japanese Utility Model Application Publication No. 5-2098, fixing work to the airtight waterproof tape is easy although the number of parts increases. Further, because fixing strength to the airtight waterproof tape is intensified by existence of a flange formed at the proximal end portion of the coupling element, this is a preferable engagement tooth structure from the viewpoint of practicability.
In any one of the above-mentioned engagement tooth structures, almost all conventional clamp elements have substantially rectangular shapes and opposing side faces in adjacent nipping portions of the clamp element are parallel to each other. Its exception is the above-mentioned Germany Patent No.856881. According to this specification, each clamp element fixed to a side edge of a pair of the fastener stringers in zigzag shape is formed in the shape of a trapezoid, whose width is decreased gradually toward a front end of the nipping portion when seen in side view.
Because the front end faces of the nipping portions of the clamp element disposed such that they oppose each other are disposed being shifted completely in the tape direction, they do not have any overlapping opposing faces. Thus, necessary contact pressing force between the waterproof tapes is not generated and airtight waterproof performance is reduced because no direct pressure force is applied to the airtight waterproof tape by the respective front end faces of the opposing nipping portions of the clamp element.
In the meantime, in the airtight waterproof slide fastener of this type, products with this fastener such as a diving suit may be folded or left without being tidied up, and be trod when they are not used. At this moment, the fastener stringer of the airtight waterproof slide fastener is folded between the engagement teeth at the same time. FIG. 7 shows a folding condition of a fastener stringer 108 at this moment. FIG. 7A is a front view of the same fastener stringer 108, while FIG. 7B is a plan view of major parts of the same fastener stringer 108 when seen from a folded side i.e., an inner side of the folded stringer.
Because the nipping portion of an ordinary clamp element provides a rectangular shape when seen in side view thereof as described above, the outside ridgelines of opposing nipping pieces 105a in the clamp elements 104 adjacent to each other on the folded side make a firm contact while the outside ridgelines of nipping pieces 105b on an opposite side across an airtight waterproof tape 101 of the clamp element 104 are about to open largely in the longitudinal direction of the tape with respect to the contact portion between the outside ridgelines on the folded side of the nipping pieces 105a. 
That is, because of the turning around an outside ridgeline of the nipping portion 105 in the clamp element 104, compression stress is applied to the airtight waterproof tape portion on a side in which the outside ridgelines make a firm contact while a strong tensile stress is applied to an airtight waterproof portion located between the outside ridgelines on the opposite side across the same tape 101 at the same time. Consequently, the airtight waterproof tape portion on the side in which the tensile stress is applied is torn out easily. This rapture of the airtight waterproof tape 101 loses the airtight waterproof performance, which should be a primary function of the airtight waterproof slide fastener 100.
The present invention has been achieved to solve the above-described problem and a concrete objective of the invention is to provide an airtight waterproof slide fastener of this kind capable of securing air-tightness and which is not broken easily even if it is bent strongly in the longitudinal direction.
The inventors have repeated discussions and experiments from various aspects in order to achieve the above objective. As a result, they recognized that it is effective to employ the structure as follows.
According to its basic structure, there is provided an airtight waterproof slide fastener having a pair of fastener stringers in which a side edge of an airtight waterproof tape wraps and holds plurality of coupling elements from flange sides, makes their coupling heads project outward, and is folded so as to form an engagement tooth holding portion having a substantially xcexa9-shaped cross section on the side edge of the tape and a peripheral face of this engagement tooth holding portion is nipped and fixed with a substantially U-shaped clamp element constituted of a nipping portion comprised of a pair of sheet-like nipping pieces and a connecting portion for connecting ends of respective nipping pieces, wherein the clamp element comprises a stress-releasing portion for releasing tensile stress generated in a tape portion existing between side faces of adjacent nipping pieces when the airtight waterproof tape is folded between adjacent clamp elements.
When the tape face of the airtight waterproof slide fastener of this kind having a conventional ordinary structure is folded in the longitudinal direction of the airtight waterproof tape, the outside ridgelines of opposing nipping pieces of adjacent clamp elements on the folded side make a firm contact and the clamp element is turned around the contact portion of the outside ridgelines, so that the same tape is opened largely between the outside ridgelines opposite to the folded side of the airtight waterproof tape. At this time, the contact portion of each outside ridgeline making a firm contact is locked and not moved relatively, so that the center of turning is fixed. Consequently, the folded airtight waterproof tape receives a large tensile stress in the longitudinal direction on an opposite side to the folded side between both clamp elements, so that it is broken out.
Thus, according to the present invention, a stress-releasing portion is formed to release excessive tensile stress generated partly in a tape portion located between the nipping portions on the front and rear face sides of the clamp element, which wraps and holds the airtight waterproof tape substantially in a C-shape. Consequently, when the airtight waterproof slide fastener is folded as described above, the firm contact position between the ridgeline portions is allowed to be moved relatively because of existence of the stress-releasing portion, so as to release excessive tensile stress between the nipping pieces at the opposite side of the folded side. As a result, no excessive tensile stress is generated in the ridgeline opposite to the folded side, so that a rapture of the airtight waterproof tape at that position is avoided effectively.
Further, according to the present invention, it is preferable that front end faces opposing each other of the nipping portions disposed such that they oppose in a zigzag shape at a predetermined pitch along opposing edge portions of a pair of the fastener stringers when the engagement teeth are coupled, are partly overlapped.
Generally, the clamp element has lip portions, which are formed on opposing end faces on front and rear nipping pieces such that they are projected so as to approach each other. When the engagement tooth portion of the airtight waterproof tape bent substantially in a xcexa9 shape is nipped strongly by means of the front and rear nipping pieces by fastening the clamp element, the lip portions provided inward protrudedly at the front ends of the nipping pieces bite into the engagement tooth holding portion so as to enhance the fixing thereof.
According to experiments by the inventors of the present invention, when the front face of the lip portion is formed in an appropriate size, even if a tongue projected to an opposite side to the lip portion is not formed at a front end of the nipping portion, necessary contact pressing force can be applied to bent portions of the airtight waterproof tapes, said bent portions being exposed outward and opposing each other, by means of pressure forces by front faces of the lip portions which generate when the airtight waterproof slide fastener is fastened. Consequently, it was proved that a sufficient air-tightness is secured.
On the other hand, the clamp element is fixed to each fastener stringer so that the front faces of the lip portions are disposed so as to oppose each other in a zigzag shape at a predetermined pitch along the opposing edge portions of a pair of the fastener stringers, when the engagement teeth are coupled. However, as described in the Germany Patent No. 856881, if the opposing faces of the clamp elements are shifted in the longitudinal direction of the tape, so that there is no overlapping portion to which the pressure force should be directly applied, no sufficient contact pressing force is generated on exposed opposing edges between the airtight waterproof tapes of a pair of the fastener stringers. Thus, according to the present invention, the opposing faces of the clamp elements, which are arranged so as to oppose each other in a zigzag shape, are disposed so as to partly overlap each other always. In this way, necessary contact pressing force between the airtight waterproof tapes are ensured and thereby airtight waterproof performance of the airtight waterproof slide fastener is enhanced.
Further, according to the present invention, it is preferable that the stress-releasing portion includes a tapered face in which, in plan view of the clamp element, the width of the side face of the nipping portion is decreased gradually at a predetermined angle in a direction from an end face on the connecting portion side of the clamp element toward a front end of the nipping portion with a start position, which is on a front end side from a position whose distance from the end face on the connecting portion is determined by summing up the thickness of the clamp element and the thickness of the airtight waterproof tape.
If the tape face of the airtight waterproof tape of the airtight waterproof slide fastener is folded in a longitudinal direction, the outside ridgelines on the nipping pieces on the folded side of the adjacent nipping portions located at a portion to be folded make a firm contact with each other as described above, so that the nipping portion is turned with that contact portion as a fulcrum point. Consequently, a large tensile stress is generated at the airtight waterproof tape located opposite to the folded side and between the adjacent clamp elements. If the nipping portion of the clamp element is rectangular in plan view as a conventional clamp element is, when the airtight waterproof slide fastener is folded as described above, the front end of the nipping portion of the clamp element is located on a tape main body side of the overlapping airtight waterproof tape, while the connecting portion side of the clamp element is located at a free end side of the airtight waterproof tape. Therefore, the folding configuration in the longitudinal direction of the tape is similar to a part of a substantially cylindrical shape in which the connecting portion side is stretched while the front end side of the nipping portion is compressed.
As a result, the clamp elements make a firm contact at the outside ridgeline portions on the front end side of the adjacent nipping portions with the folding portion of the airtight waterproof slide fastener as the center, the side faces on the connecting portion side are slightly open. In this situation, little internal stress is generated inside the folded portion of the engagement tooth holding portion in the airtight waterproof tape folded at the base portion side of the coupling element, while an excessive tensile stress is generated so as to stretch the outside of the folded portion largely.
The present invention is achieved with focus on the above-described folding configuration. At first, it was considered that the stress-releasing portion could be made by providing right and left side faces of the nipping portion of each clamp element each with a tapered face whose front end side becomes narrower gradually like the above-described substantial cylindrical shape. However, according to the fixing structure of the engagement tooth to the airtight waterproof tape of the present invention, as mentioned above, the clamp element is bent and fixed to the airtight waterproof tape so that the airtight waterproof tape and the clamp element wrap and hold the coupling element.
To nip the airtight waterproof tape strongly with the entire nipping portions of the clamp element with such a fixing structure, it is preferable to ensure at least the same nipping force at a border face between the nipping portion and the connecting portion as that of conventional ones. For this purpose, as in the present invention, at least the airtight waterproof tape""s engagement tooth holding portion bent substantially in a C-shape and the border face from the connecting portion of the clamp element up to the nipping portion need to have a similar width in the longitudinal direction of the tape to that of conventional ones. Thus, in the present invention, the start point of the tapered face, whose width is reduced gradually toward the front end of the nipping portion, is set up at a position determined by summing up the thickness of the clamp element and the tape thickness of the airtight waterproof tape.
According to the present invention having the above-mentioned structure, a fixing strength necessary for the engagement tooth to fix the airtight waterproof slide fastener is secured, and when the airtight waterproof slide fastener is folded in a longitudinal direction, the tapered face serves as a stress-releasing portion, so as to avoid an interference to each other. Even if the outside ridgeline portions make a contact, they are just only in a slight contact when the folding is completed. Thus, no excessive tensile stress is generated in an airtight waterproof tape portion existing between a nipping portion opposite to the folded side and the connecting portion, so that rapture in the airtight waterproof tape portion can be avoided.
Preferably, the tapered angle of the tapered face on both side faces of the clamp element is 3xc2x0 to 7xc2x0 as in the present invention. If the tapered angle is less than 3xc2x0, the outside ridgeline portions of the adjacent nipping pieces on the folded side make a firm contact with each other so that they are locked. Consequently, the function as the stress-releasing portion is not exerted sufficiently, so that rapture is easily generated in the airtight waterproof tape between the clamp elements on a folding side i.e., an outer side of the folded stringer. Meanwhile, if the tapered angle exceeds 7xc2x0, a direct pressure force, which is applied to between the clamp elements disposed such that they oppose each other, is unlikely to be generated when the airtight waterproof slide fastener is fastened. Thus, the contact pressing force between the opposing airtight waterproof tapes is not generated effectively, and obtaining necessary air-tightness performance becomes difficult.
Further, it is preferable that the stress-releasing portion includes chamfered portions on the peripheral face of the front end-side corner portion of the nipping portion. In addition, it is preferable that the stress-releasing portion includes a chamfered portion formed on outside ridgeline portions of the nipping portion. Moreover, the stress-releasing portion including a chamfered portion formed at least on an end portion of the inside ridge line portion of the nipping portion is formed in some cases.
Any of these stress-releasing portions can avoid effectively rupture of a part of the airtight waterproof tape between the clamp elements around the folded portion when the airtight waterproof slide fastener is bent in a longitudinal direction.